I should clarify what I said: the actual gameplay footage has serious framerate issues. The in-game cut scenes (which appears to be the lion's share of that trailer) was pretty smooth.

A perfect example of this is when the camera switches from cut scene view to 3rd person when they jump in the hovercraft. That is a point that I believe is definately actual gameplay footage and the framerate drops horribly at that point. It's at 0:37 of the video. Jumping over those crates at 0:53 is pretty bad too.

Again though, most of that video is not actual gameplay which means that it doesn't tell us what the game really looks like or how it really plays. I honestly do not think that any of it is real-time in-game footage. Notice how it's never from a playable viewing angle and there are never any crosshairs, huds, etc.?